This invention relates in general to radiant energy collecting or emitting apparatus, and in particular relates to radiant energy absorber/emitter elements of the flat plate type and methods and tools for the manufacture thereof.
Various types of flat plate radiant energy collecting and emitting devices have heretofore been provided. Among these devices are flat plate solar energy collectors in which flat metal plates exposed to solar energy are formed integral with or are connected to tubes or pipes through which a heat exchange fluid is directed. One example is U.S. Pat. No. 3,448,798 to Coe which provides a method for attaching coolant tubing to the surface of a thermal energy conducting element.
In many cases it is desirable to form the solar energy collecting plate of a material having good heat conduction properties but which is relatively inexpensive, such as aluminum, while forming the heat exchange fluid tubing of another material also having good thermal conduction properties but which is more compatible with the fluid, such as copper. In such cases it has been difficult to assemble the tubing on the plate so that there is intimate heat exchange contact at the surfaces for maximizing heat flow. One problem which has been encountered is that where the plate is extruded from metals such as aluminum it is not possible to control close tolerances inexpensively so that a close fit between the tubing and plate is not easily attained. In an arrangement in which projections on a plate are swaged about the tubing, as in the above-mentioned Coe patent, an opening is formed at the seam along the swaged projections such that moisture, oxygen or other matter can enter through the seam and spread between the tubing and plate to cause oxidation and the like which attenuates heat transfer. Another problem is that the tubing can displace relative to the plate under changing thermal and mechanical stresses so that there is a loss in surface contact and further attenuation in heat conduction between the tubing and collector plate.